Automatic active/passive fuze system

ABSTRACT

1. A radio fuze system comprising means for transmitting a radio frequency signal in the direction of a target, first antenna means for receiving only the reflected signals transmitted by said transmitting means, a firing circuit, circuit means coupling said first antenna means to said firing circuit for providing an initiating signal thereto when said received signal has a magnitude of a predetermined value, second antenna means for receiving countermeasures signals, and means coupled to said second antenna means for causing said fuze system to respond to said countermeasures signals to prevent dudding past the target.

Unite States atet 1191 1111 3,924,234

Cash et al. 1 Dec. 2, 1975 [54] AUTOMATIC ACTIVE/PASSIVE FUZE 3,732,5645/1973 Kuck et al 343/7 PF SYSTEM 3,747,531 7 1973 Powell 102/702 P [75]Inventors: Carlton H. Cash, Norco; Robert A.

Boot Riverside; Ralph Bauer, Primary Examiner-Malcolm F. HublerRiverside; Benjamin Husten, Attorney, Agent, or FirmRichard S. Sciascia;Joseph Riverside, 3]] of Calif M. St. Amand; T. M. Phillips [73]Assignee: The United States of America as represented by the Secretaryof the EXEMPLARY CLAIM Navy, Washington, DC.

1. A rad1o fuze system comprlsing means for transm1t- Flledl 27, 1960ting a radio frequency signal in the direction of a tar- [21] APP]78,767 get, first antenna means for receiving only the reflected signalstransmitted by said transmitting means, a firing circuit, circuit meanscoupling said first anl l Cl 343/7 3431/l8 E tenna means to said firingcircuit for providing an inil l F42C 13/04; G015 7/36; G015 9/02;tiating signal thereto when said received signal has a HO4K 3/00magnitude of a predetermined value, second antenna Field M Search 343/7,13, 12, 17-1, means for receiving countermeasures signals, and

343/7 PF, 18 E; 102/701 P means coupled to said second antenna means forcausing said fuze system to respond to said countermea- TRANSMITTER l lReferences Cited sures signals to prevent dudding past the target.UNITED STATES PATENTS 3,219,826 11/1965 Letaw, Jr 102/702 P 8 Clams 3Drawmg F'gures 72 75 74 NORD 7 Q- E ZQT T q FIRING CIRCUIT DETECTOR 1 ll 77 7e MIXER 80 l l r 73h 79 I 1 Allli l'piER AND FIRING CIRCUIT 7DETECTOR I 8| 1 1 1 t as 3 j s4 82 T AM tllllzrt MIXER -v= AND DETECTOR7| V as 7o 85 US. Patent Dec. 2, 1975 Sheet 1 of 3 3,924,234

I2 NORD AMPLIFIER FILTERS AND DETECTOR FIRING CIRCUIT 25 PASSIVEAMPLIFIER AND DETECTOR GUARD AMPLIFIER A AND MIXER DETECTOR TRANSMITTERFiGii CARLTON H. CASH ROBERT A. BOOT RALPH L. BAUER BENJAMIN F. HUSTENIN V EN TORS ATTORNEYS UB. Patent Dec. 2, 1975 Sheet 3 01 3 3,924,234

K NTL FIRING CIRCUIT DETECTOR l AM R L IQ ER DETECTOR 7| if 88 m '1TRANSMITTER CARLTON H. CASH ROBERT A. BOOT RALPH L. BAUER BENJAMIN F.HUSTEN IN VENTORS BY gj aw/kw ATTORNEYS AUTOMATIC ACTIVE/PASSIVE FUZESYSTEM The invention herein described may be manufactured and used by orfor the Government of the United States of America for governmentalpurposes without the payment of any royalties thereon or therefor.

The present invention relates to an automatic active/- passive fuzesystem and more particularly to an automatic active/passive fuze systemwhich eliminates possibility of jammer saturation and subsequent dangerof fuze dudding.

In known systems, for example the system shown and described inapplication Ser. No. 789,459, filed Jan. 27, 1959 by Carlton I-I. Cash,dudding can be caused by jammer saturation of the detector circuit.Saturation can be caused by reception of a countermeasures signal of thesame frequency and strength as the illuminating signal being transmittedby the fuze circuit.

Accordingly, an object of the present invention is the provision ofreliable automatic fuzing of guided missile warheads in presence orabsence of severe countermeasures environment.

Another object is to provide a fuze system which utilizes jamming energyin conjunction with normal fuze active energy to assure optimum burstlocalization.

Other objects and many of the attendant advantages of this inventionwill become readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

FIG. 1 is a generic block diagram illustrating the principle ofoperation of the invention.

FIG. 2 is a block diagram of a fuze system emboding the invention.

FIG. 3 is a block diagram of another embodiment of the invention.

Referring now to FIG. 1, there is shown a transmitter having an antennasystem 11 coupled thereto for radiating radio frequency energy. Nordamplifier filters and detector 12 and passive amplifier and detector 13are each connected, to antenna system 14 through a portion ofpotentiometer 16 and mixer 17. Nord amplifier filters and detector 12 isconnected to firing circuit 18 through a portion of potentiometer 19while passive amplifier and detector 13 is connected to firing circuit18 through relay switch 20 and potentiometer actuating coil 25. Guardamplifier and detector 21 is connected to antenna 22 through mixer 23and to ground through relay coil 24 and potentiometer actuating coil 26respectively.

The principal of operation is as follows: In the absence ofcountermeasures (quiet target), transmitter 10 radiates radio frequencyenergy through antenna system 11 which should have a narrow beam conicalpattern to illuminate a target upon intercept. Re-radiated energy from atarget (not shown) is received through antenna system 14 which hasidentical beam characteristics to antenna system 11. Energy thusreceived is mixed in mixer 17 with an attenuated portion of thetransmitted signal by means of coupler 15 to generate a dopplerfrequency which is detected and amplified in circuit 12 and then fed tofiring circuit 18 through a portion of potentiometer 19. Provided thetarget is within a predetermined fuzing range, a signal of sufficientmagnitude will be fed to firing circuit 18 to cause detonation of awarhead.

In the case of an off-target jammer, threshold energy levels resultingfrom countermeasures will be received by antenna system 14 only when thejammer signal is in the main lobe of the antenna pattern. This energywill be mixed in mixer 17 to generate frequencies which will be detectedin both nord amplifier filters and detector 12 and passive amplifier anddetector 13. However, the signal output from circuit 13 flowing in coil25 actuates potentiometer 19 so that the output of circuit 12 isprevented from reaching firing circuit 18. Target doppler signalsexisting at the output of mixer 17 of FIG. 1 occur over a specified andlimited band of frequencies. Signals such as ECM signals not referencedto the randomly modulated signal transmitted from antenna 11 will uponcross-correlation at mixer 17 with a portion of the transmitted signalgenerate mixer output frequency components extending over a much widerband of frequencies than the dopplers from target reflected components.The presence of energy in amplifier 13 can be construed to be other thanwithin fuzing range target reflected energy and is used to actuatepotentiometer 19 through coil 25 to prevent false alarm firing.Amplifiers 12 and 13 may be of the type shown and described on pp837-849 in Introduction to Statistical Communication Theory, DavidMiddleton, New York; McGraw-Hill (1960).

In the case of an on-target jammer (noisy target) countermeasures energyis received through antenna system 22 and antenna system 14 front sidelobes. The antenna pattern characteristics of antenna system 22 may beeither omidirectional, forward-looking solid cone, narrow-beam conicalinclined forward of antenna 14 main lobe, or variations of these.Countermeasures energy received through antenna system 22 is processedthrough mixer 23 and amplifier detector 21 and applied to relay coil 24and potentiometer actuating coil 26. A portion of the signal transmittedis coupled by coupler 30 to mixer 23 to provide the reference signal.The sensitivity level of antenna system 22, mixer 23, amplifier detector21, and actuating coil 26 is set such that countermeasures energyentering the front side lobes of antenna system 14 will be attenuated bypotentiometer 16 so that the threshold level is not reached at theoutputs of nord amplifier filters and detector and passive amplifier anddetector 13. The function of relay 24 is to disable amplifier detector13 through relay switch 20 when the output from amplifier detector 21reaches a predetermined level so that detonation can occur whensufficient countermeasures energy enters amplifier and detector circuit12. At intercept the jammer will enter the main lobe of antenna system14 thus increasing the signal fed to amplifier and detector circuit 12sufficiently to activate firing circuit 18.

In the event jammer power is cut off (blinking jammer) after havingpreviously caused the fuze system to become passive in operation, theoutput from circuit 21 would decrease, thus, causing relay 20 switch toclose and potentiometer 16 to return to its original position. The fuzesystem then is restored to full active capability.

Referring now to FIG. 2 there is shown a transmitter coupled to anantenna 51 for radiating radio frequency energy. An active channelconsisting of receiving antenna 52, mixer 53, active/passive IFamplifier 54 and Nord amplifier filter and detector 56 is connected asone input to firing circuit 58. A passive channel consisting ofreceiving antenna 52, mixer 53, active/passive IF amplifier 54 andpassive amplifier and detector 57 is connected through switch S1 as asecond input to firing circuit 58. A guard channel for operating relay59 consists of receiving antenna 61, mixer 62, guard IF amplifier 63,guard amplifier and detector 64 and relay coil 66. An automatic gaincontrol circuit 65 is connected respectively between S2 of relay 59 andactive/- passive IF amplifier 54 and guard IF amplifier 63. This AGCfunctions causes the sensitivity of the active/passive IF amplifier 54and Guard IF amplifier 63 to be automatically adjusted in accordancewith the jammer power being received such that the fuze functions onlywhen the on-target jammer enters the main beam of antenna 52. Thisassures burst control so that warhead damage is maximum regardless ofthe amount of jamming power being radiated. Coupling 67 is provided tofeed a portion of the transmitted energy from transmitter 50 to mixers53 and 62. V

In operation, with the absence of electrical countermeasures, the activechannel functions in the same manner as the system shown and describedin Ser. No. 789,459 previously mentioned. However, in the presence ofelectrical countermeasures, the signal received by antenna 61 issufficient to produce an output signal from guard amplifier and detector64 to actuate relay 59 to the closed position. This connects the passivechannel to firing circuit 58 thereby permitting firing circuit 58 to beinitiated by the countermeasures signal which has already made theactive system in-operative. The sensitivity of IF amplifiers 54 and 63are controlled by AGC circuit 65 so that switching from active topassive operation will be accomplished at desired signal strengthsreceived by antennas 52 and 61. In the event jammer power is cut offafter having previously caused the fuze system to become passive inoperation, relay 59 and automatic gain control circuits areautomatically de-activated thus restoring full active capability to thefuze system.

Referring now to FIG. 3 there is shown a transmitter 70 having anantenna system 71 coupled thereto for radiating radio frequency energy.Nord amplifier filters and detector 72 and passive amplifier anddetector 73 are each connected to receiving antenna 74 through mixer 76and a portion of potentiometer 77. Amplifier and detecting circuit 72 isconnected to firing circuit 75 through relay switch 78 while amplifierand detecting circuit 73 is connected to firing circuit 79 through relayswitch 81 and to ground through relay coil 80. Amplifier and detectingcircuit 82 is connected to guard antenna 83 through mixer 84 and toground through relay coil 86 and potentiometer actuating coil 87respectively.

Antenna systems 71, 74 and 83 have the same transmitting and receivingcharacteristics respectively as antenna systems 11, 14 and 22 of FIG. 1.Re-radiated energy from a target (not shown) is received through antennasystem 74. In the absence of countermeasures, the received energy iscoherent and is mixed in mixer 76 with a signal from transmitter 70 bymeans of coupler 85 to generate a frequency which is detected andamplified in circuit 72 and then fed to firing circuit 75 through relay78. Provided the target is within a predetermined fuzing range, firingcircuit 75 is initiated by the output from amplifier and detectingcircuit 72, which in turn causes warhead detonation.

In the case of an off-target jammer, threshold energy levels resultingfrom countermeasures will be by antenna 74 only when the jammer signalis in the main lobe of the antenna pattern. This energy which isincoherent is mixed in mixer 76 and amplified and detected in bothcircuits 72, 73. Sensitivity levels of circuits 72, 73 are set such thatthe output signal of amplifier detecting circuit 73 flowing in relaycoil opens relay 78 and prevents the output of circuit 72 from reachingfiring circuit 75.

In the case of an on-target jammer countermeasures energy is receivedthrough antenna 83 and through the front side lobes of antenna 74.Countermeasures energy received through antenna system 83 is processedthrough mixer 84 and amplifier detector 82 and applied to relay coil 86and potentiometer actuating coil 87. A portion of the signal transmittedis coupled by coupler 88 to mixer 84 to provide the reference signal.The sensitivity level of antenna system 83, mixer 84, amplifier detector82, and relay coil 86 is-set such that relay switch 81 will be closedwhen countermeasures become sufficiently strong to enter the front sidelobes of antenna system 74. The sensitivity level of antenna system 83,mixer 74, amplifier detector 82 and coil 87 is set such that the energylevel (due to countermeasures signal in front side lobes of antennasystem 74) in amplifier detector 73 will be insufficient to activatefiring circuit 79. However, when the jammer signal enters the main lobeof antenna system 74 and leaves the forward looking lobe of antennasystem 83, there is a sharp shift in the relative amount of energy inamplifier detectors 82 and 73. This is because the decrease of energy inamplifier detector 82 will allow control coil to be deactivated(decreasing the resistance of potentiometer 77 to the incoming signal)at the same time a large increase in gain of the signal received inantenna system 74 occurs. Thus, the energy in amplifier detector 73 issufficient to activate firing circuit 79. In the event the jammer signalis cut off after having previously caused the fuze system to becomepassive in operation, potentiometer 77, relay '78 and relay 81automatically deactivate thus restoring full active capability to thefuze system.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. A radio fuze system comprising means for transmitting a radiofrequency signal in the direction of a target, first antenna means forreceiving only the reflected signals transmitted by said transmittingmeans, a firing circuit, circuit means coupling said first antenna meansto said firing circuit for providing an initiating signal thereto whensaid received signal has a magnitude of a predetermined value, secondantenna means for receiving countermeasures signals, and means coupledto said second antenna means for causing said fuze system to respond tosaid countermeasures signals to prevent dudding past the target.

2. A radar fuze system comprising means for transmitting a radiofrequency signal in the direction of a target, first antenna means forreceiving reflected signals transmitted by said transmitting means, afiring circuit, active circuit means coupling said first antenna meansto said firing circuit for providing an initiating signal thereto whensaid received signal has a magnitude of a predetermined value, secondantenna means for receiving countermeasures signals, and circuit meanscoupled to said second antenna means for rendering said active circuitmeans passive whereby said fuze system will respond to saidcountermeasures signal for optimum firing.

3. A radar fuze system comprising means for transmitting a radiofrequency signal in the direction of a target, first circuit meansresponsive to said transmitted signal after being reflected from saidtarget for initiating a firing signal for said fuze system, secondcircuit means responsive to electronic countermeasures signals forpreventing said first circuit means from becoming saturated by saidcountermeasures signals.

4. A radar fuze system comprising means for transmitting a radiofrequency signal in the direction of a target, first circuit meansresponsive to said transmitted signal after being reflected from saidtarget for initiating a firing signal for said fuze system, secondcircuit means responsive to electronic countermeasures signals forrendering said first circuit means nonresponsive to said transmittedsignal and responsive to said countermeasures signals whereby dudding isprevented in the lethal range of said target.

5. A radar fuze system comprising means for transmitting a radiofrequency signal in the direction of a target, an active/passive circuitnormally operating in the active phase responsive to said transmittedsignal after being reflected from said target for initiating a firingsignal for said fuze system, guard circuit means responsive toelectronic countermeasures signals and having an output proportional tothe signal strength of said countermeasures signal, and switch meansresponsive to the output of said guard circuit means for switching saidactive/passive circuit means from its normal active phase to its passivephase when the amplitude of said guard circuit output reaches apredetermined amplitude.

6. A radar fuze system comprising transmitter means including an antennasystem for transmitting a radio frequency signal in a narrow beamconical pattern in the direction of a target, a first receiving antennahaving identical beam characteristics to said transmitting antenna forreceiving re-radiated energy from the target, first mixer means coupledto said first receiving antenna and to said transmitter means forgenerating a doppler output signal, firing circuit means having firstand second inputs, active amplifier and detector circuit means coupledto said first mixer means for generating an output signal proportionalto the proximity of the target, passive amplifier and detector circuitmeans coupled to said first mixer means for generating an output signalproportional to the proximity of a countermeasures signal, circuit meanscoupling the output of said active amplifier and detector circuit meansdirectly to the first of said firing circuit inputs, circuit meansincluding a switch having a first and second position coupling theoutput of said passive amplifier and detector circuit means to thesecond of said firing circuit inputs, a second receiving antenna havingbeam characteristics which excludes the signal transmitted from saidtransmitter and receptive to all other signals of the operatingfrequency of said fuze system, second mixer means coupled to said secondreceiving antenna and to said transmitter means for generating a doppleroutput signal, guard amplifier and detector circuit means coupled tosaid second mixer means for generating an output signal proportional tocountermeasures signals received in said second receiving antenna,switch actuating means coupled to said guard amplifier and detectorcircuit means for actuating said switch from said first position to saidsecond position when the output signal of said guard amplifier anddetector reaches a pre-determined value, whereby said passive amplifierand detector is connected to the second input of said firing circuit.

7. The system of claim 6 including means for controlling the thresholdvalue at which the system is switched from active to passive in thepresence of countermeasures signals.

8. A radar fuze system comprising means for transmitting a radiofrequency signal in the direction of a target, first and second firingcircuits first circuit means coupled to said first firing circuitincluding a first receiving antenna responsive to said transmittedsignal after being reflected from said target for generating a firingsignal to initiate said first firing circuit, second circuit meanscoupled to said first and second firing circuits including a secondreceiving antenna for de-' activating said first firing circuit andactivating a second firing circuit in response to receivedcountermeasures signals, and third circuit means including said secondfiring circuit responsive to said countermeasures signals received insaid first receiving antenna for initiating said second firing circuit.

1. A radio fuze system comprising means for transmitting a radiofrequency signal in the direction of a target, first antenna means forreceiving only the reflected signals transmitted by said transmittingmeans, a firing circuit, circuit means coupling said first antenna meansto said firing circuit for providing an initiating signal thereto whensaid received signal has a magnitude of a predetermined value, secondantenna means for receiving countermeasures signals, and means coupledto said second antenna means for causing said fuze system to respond tosaid countermeasures signals to prevent dudding past the target.
 2. Aradar fuze system comprising means for transmitting a radio frequencysignal in the direction of a target, first antenna means for receivingreflected signals transmitted by said transmitting means, a firingcircuit, active circuit means coupling said first antenna means to saidfiring circuit for providing an initiating signal thereto when saidreceived signal has a magnitude of a predetermined value, second antennameans for receiving countermeasures signals, and circuit means coupledto said second antenna means for rendering said active circuit meanspassive whereby said fuze system will respond to said countermeasuressignal for optimum firing.
 3. A radar fuze system comprising means fortransmitting a radio frequency signal in the direction of a target,first circuit means responsive to said transmitted signal after beingreflected from said target for initiating a firing signal for said fuzesystem, second circuit means responsive to electronic countermeasuressignals for preventing said first circuit means from becoming saturatedby said countermeasures signals.
 4. A radar fuze system comprising meansfor transmitting a radio frequency signal in tHe direction of a target,first circuit means responsive to said transmitted signal after beingreflected from said target for initiating a firing signal for said fuzesystem, second circuit means responsive to electronic countermeasuressignals for rendering said first circuit means non-responsive to saidtransmitted signal and responsive to said countermeasures signalswhereby dudding is prevented in the lethal range of said target.
 5. Aradar fuze system comprising means for transmitting a radio frequencysignal in the direction of a target, an active/passive circuit normallyoperating in the active phase responsive to said transmitted signalafter being reflected from said target for initiating a firing signalfor said fuze system, guard circuit means responsive to electroniccountermeasures signals and having an output proportional to the signalstrength of said countermeasures signal, and switch means responsive tothe output of said guard circuit means for switching said active/passivecircuit means from its normal active phase to its passive phase when theamplitude of said guard circuit output reaches a predeterminedamplitude.
 6. A radar fuze system comprising transmitter means includingan antenna system for transmitting a radio frequency signal in a narrowbeam conical pattern in the direction of a target, a first receivingantenna having identical beam characteristics to said transmittingantenna for receiving re-radiated energy from the target, first mixermeans coupled to said first receiving antenna and to said transmittermeans for generating a doppler output signal, firing circuit meanshaving first and second inputs, active amplifier and detector circuitmeans coupled to said first mixer means for generating an output signalproportional to the proximity of the target, passive amplifier anddetector circuit means coupled to said first mixer means for generatingan output signal proportional to the proximity of a countermeasuressignal, circuit means coupling the output of said active amplifier anddetector circuit means directly to the first of said firing circuitinputs, circuit means including a switch having a first and secondposition coupling the output of said passive amplifier and detectorcircuit means to the second of said firing circuit inputs, a secondreceiving antenna having beam characteristics which excludes the signaltransmitted from said transmitter and receptive to all other signals ofthe operating frequency of said fuze system, second mixer means coupledto said second receiving antenna and to said transmitter means forgenerating a doppler output signal, guard amplifier and detector circuitmeans coupled to said second mixer means for generating an output signalproportional to countermeasures signals received in said secondreceiving antenna, switch actuating means coupled to said guardamplifier and detector circuit means for actuating said switch from saidfirst position to said second position when the output signal of saidguard amplifier and detector reaches a pre-determined value, wherebysaid passive amplifier and detector is connected to the second input ofsaid firing circuit.
 7. The system of claim 6 including means forcontrolling the threshold value at which the system is switched fromactive to passive in the presence of countermeasures signals.
 8. A radarfuze system comprising means for transmitting a radio frequency signalin the direction of a target, first and second firing circuits firstcircuit means coupled to said first firing circuit including a firstreceiving antenna responsive to said transmitted signal after beingreflected from said target for generating a firing signal to initiatesaid first firing circuit, second circuit means coupled to said firstand second firing circuits including a second receiving antenna forde-activating said first firing circuit and activating a second firingcircuit in response to received counter-measures signals, and thirdcircuit means including said second firing circuiT responsive to saidcountermeasures signals received in said first receiving antenna forinitiating said second firing circuit.